[mpiwg-p2p] Meeting Today?

[Dan Holmes]

Hi Jeff,

I wrote some notes about our discussion.
https://github.com/mpiwg-p2p/p2p-issues/wiki/notes-2017-03-27 <https://github.com/mpiwg-p2p/p2p-issues/wiki/notes-2017-03-27>

In short, the memory must be returned to the original owner for de-allocation.
We mentioned an attach/detach method for using user memory.
We also discussed using Fsend/Arecv to/from MPI_COMM_NULL to transfer ownership without needing another message.
This needs careful thought - hence the suggestion for sequence diagrams.

Cheers,
Dan.

> On 27 Mar 2017, at 22:42, Jeff Hammond <jeff.science at gmail.com> wrote:
> 
> Actually, it has to be required in the literal sense.
> 
> Fsend frees memory. Has to know which allocator used. MPI_Alloc_mem is the only one MPI knows about. 
> 
> Same in reverse for Arecv and MPI_Free_mem.
> 
> How else can you do it? We could register callbacks for memory allocator but that will almost certainly prevent every useful optimization. 
> 
> Jeff
> 
> Sent from my iPhone
> 
> On Mar 27, 2017, at 8:57 AM, Dan Holmes <d.holmes at epcc.ed.ac.uk <mailto:d.holmes at epcc.ed.ac.uk>> wrote:
> 
>> “required” is possibly too strong. “advisable” would be closer to my expectation. “needed in order for MPI to enable all possible optimisations” is more wordy/precise.
>> 
>> Cheers,
>> Dan.
>> 
>>> On 27 Mar 2017, at 16:55, Jeff Hammond <jeff.science at gmail.com <mailto:jeff.science at gmail.com>> wrote:
>>> 
>>> No. MPI_Alloc_mem and MPI_Free_mem were going to be required. At least that was my plan. 
>>> 
>>> Sent from my iPhone
>>> 
>>> On Mar 27, 2017, at 8:51 AM, Jim Dinan <james.dinan at gmail.com <mailto:james.dinan at gmail.com>> wrote:
>>> 
>>>> Did we previously look at using MPI_Buffer_attach as a way to support allocate-and-recv?
>>>> 
>>>> On Mon, Mar 27, 2017 at 11:38 AM, Jeff Hammond <jeff.science at gmail.com <mailto:jeff.science at gmail.com>> wrote:
>>>> I'm on vacation but I endorse other people doing stuff with Fsend-Arecv, since the slacker who owned it for the past two years hasn't made any progress. I think I copied all the relevant content to GitHub already.
>>>> 
>>>> Jeff
>>>> 
>>>> Sent from my iPhone
>>>> 
>>>> > On Mar 27, 2017, at 8:16 AM, Dan Holmes <d.holmes at epcc.ed.ac.uk <mailto:d.holmes at epcc.ed.ac.uk>> wrote:
>>>> >
>>>> > Hi Jim, et al,
>>>> >
>>>> > I was hoping to move the WG on to talking about Freeing-Send and Allocating-Receive (Fsend & Arecv).
>>>> >
>>>> > I’d like to re-boot and refresh caches on that with a goal of presenting something (probably informally) next face-to-face meeting in June.
>>>> >
>>>> > I’ll start the call and see how many turn up.
>>>> >
>>>> > Cheers,
>>>> > Dan.
>>>> >
>>>> >> On 27 Mar 2017, at 15:28, Jim Dinan <james.dinan at gmail.com <mailto:james.dinan at gmail.com>> wrote:
>>>> >>
>>>> >> Hi All,
>>>> >>
>>>> >> The info query proposal seems to be converging.  I don't think there's anything to discuss on this topic this week.
>>>> >>
>>>> >> Current status is that Pavan will check with vendors to make sure they are ok with updating MPICH to report the user's info key value instead of the effective value being used by the implementation.  Assuming this is ok, it sounds like the proposal that was read at the last meeting is ready to move forward into voting.
>>>> >>
>>>> >> Are there any other topics for discussion?  If not, I think we can cancel today's meeting.
>>>> >>
>>>> >> Cheers,
>>>> >> ~Jim.
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